Coated abrasive wheel element



2 Sheets-Sheet 1 Filed Oct. 17, 1955 nlrkaan M w E .a hm

1956 F. E. HENDIVQICKSON 2,770,927

COATED ABRASIVE WHEEL ELEMENT Filed Oct. 17, 1955 2 Sheets-Sheet 2 United States Patent COATED ABRASIVE WHEEL ELEMENT Fritz E. Hendrickson, South Eigin, 111., assignor to Norton Company, Troy, N. Y., a corporation of Massachusetts Application October 17, 1955, Serial No. 540,853

4 Claims. (Cl. 51-193) This invention relates to improvements in polishing Wheels, and more particularly to a flexible, abrasive polishing wheel element and to a method of making the same, and is a continuation-in-part of my co-pending application bearing the same title, Serial No. 388,308, filed October 26, 1953.

Previous constructions of devices for polishing work pieces, particularly pieces having contoured shapes, have been subject to certain disadvantages. These devices include solid wheels formed entirely of abrasive material or wheels having abrasive peripheries. Most of the devices have utilized abrasive surfaces having straight line or fiat area contact with the work piece. In operation, an operator manually turns the contoured piece at various angles in an attempt to bring all the surface areas thereof into contact with the moving abrasive polishing surface. As a result, the polished piece either has some inaccessible and unabraded areas or numerous areas abraded in different directions effecting an unsightly appearance.

To overcome some of the foregoing disadvantages, use has been made of travelling flexible belts having an abrasive face. Limited contouring of the belt face has been possible by engaging contact wheels with certain portions of the belt to effect a desired cross-sectional shape. Some additional deformation of the flexible belt has been possible by forcing either the belt against the work piece or the Work piece against the belt. As a result, portions of the belt are overstressed thereby materially shortening its working life. In addition, the variable and excessive pressures exerted against different portions of the belt surfaces quickly result in glazing caused by a filling or loading of the spaces between adjacent particles of abrasive material. These glazed surfaces damage the work piece either by streaking or burning the surfaces thereof and may, if the wall of the work piece is snificiently thin, result in deformation through the inadequate dissipation of the heat so generated.

In the operation of abrasive devices where excessive pressures are applied, lubricants such as water, oil, grease or the like are used to wash away material being removed by abrasion and to absorb and conduct heat from the work surface.

The device of the present invention is designed to eliminate the foregoing objections and disadvantages by the even distribution of polishing pressure over a contoured surface and by the quick dissipation of friction heat through proper ventilation. Generally, this is accomplished by presenting in wheel form the marginal edges of folded, flexible, abrasive-surfaced sheets against a work piece and effecting a bending of small marginal areas of the folds to provide a multiplicity of abrasive surfaces by rotating the wheel and moving the folded sheets over the work surface or surfaces to be polished.

Accordingly, the invention comprises a polishing device including an abrasive element adapted to be removably attached to a polishing wheel hub with the ele- 2,770,927 Patented Nov. 20, 1956 ment having one or more sheets of fibrous material coated on at least one surface with an adherent abrasive, being pleated to form wave-like edges at the ends, and then folded substantially medially thereof for application to the hub.

An important object of the invention, then, is to pro- Vide a novel polishing wheel element and a method of making the same, for uniformly polishing the surfaces of a contoured work piece.

Another object of this invention is to provide a polishing wheel element which is self-adjusting in contact with contoured work surfaces without the application of excessive pressures.

Still another object of this invention is to provide, in a flexible polishing wheel, a multiplicity of small abrasive areas for contact with a surface to be polished.

A further object of this invention is to provide a polishing wheel having flexible elements which operatively engage a contoured work surface under a uniformly distributed pressure.

A still further object of this invention is to provide flexible elements in a polishing wheel having incorporated therein a highly efficient ventilation system.

Another and still further object of this invention is to provide flexible elements for a polishing wheel having uniform polishing characteristics throughout the entire work life thereof.

Yet another object of this invention is to provide a polishing wheel having elements which are self-cleaning in operation.

A still further object of this invention is to provide elements for a polishing wheel which are simple and durable in construction, highly eflicient in use, and inexpensive in maintenance and operation.

Other and further objects of the invention will become apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings, which .disclose preferred embodiments of the invention.

On the drawings:

Figure 1 is a face view in elevation of an abrasivecoated polishing sheet before being folded along the dotted lines;

Figure 2 is an edge view of a polishing sheet folded as suggested in Figure 1;

Figure 3 is a face view in elevation of the folded polishing sheet shown in Figure 2, in which adjacent folds partially overlap;

Figure 4 is a front view in elevation of a composite plural-element polishing wheel constructed according to the principles of the present invention;

Figure 5 is a vertical cross-sectional view, with portions in elevation, taken along a plane indicated substantially by the line 55 of Figure 4 and showing details of construction of a wheel hub assembly on which the folded abrasive sheets are mounted;

Figure 6 is an enlarged edge view in elevation of a folded abrasive-coated polishing sheet as seen along that portion of the periphery of the Wheel indicated by the line 66 of Figure 4 and showing the numerous marginal edge portions bent along the wheel periphery to form abrading areas;

Figure 7 is a modified form of polishing sheet showing the provision of rows of slits provided to facilitate the bending of the marginal edge portions thereof;

Figure 8 is a view, similar to Figure 3, of a modified form of sheet in which adjacent folds completely overlap;

Figure 9 is a view, similar to Figure 2, showing the width of the folded sheet in Figure 8 as being the width of a fold.

Figure 10 is a fragmental view, partially in cross-section, showing the relative thickness of folds in bufling elements having abrasive material on the side surfaces forming the folds;

Figure 11 is a view, similar to 10, showing the folds of the bufling elements with no abrasive material on the inside surfaces, illustrating a comparison in thickness of the respective folds; and,

Figure 12 is a view, similar to Figures and 11, showing the folded arrangement of bufiing elements around a mounting pin with abrasive material only on those side portions of the elements remote from the pin.

As shown on the drawings:

Referring now in detail to the several figures, the numeral generally designates a sheet of fibrous material such as paper, cloth, or the like. A coating 21 of granular mineral substance, such as emery or other abrasive, is applied and adhesively secured to the sheet. For maximum efiiciency, both faces of the sheet are so coated. However, the herein described invention will function satisfactorily if but one face of the abrasive sheet is so coated.

In the preferred form as shown in Figures 1, 2 and 3, the abrasive-coated sheet 20 is folded along the dotted fold lines 22, 22. The fold arrangement is such that one pleat partially overlaps an adjacent pleat effecting a folded sheet of a width narrower than the unfolded sheet. As so folded, the sheet is doubled upon itself along the fold line 23 extending medially lengthwise thereof. In this folded and doubled arrangement, each of the ends of the sheet present an undulated edge outline having a wavy form with successive curves in alternate directions, as seen in Figure 6. While the abrasive-coated sheet is preferably rectangular in shape it may be of any form folded or bunched to present a wavy periphery. Also, each abrasive element may comprise any desired number of thicknesses of abrasive coated sheets in face engagement or interleaved with uncoated sheets. As so folded, each abrasivecoated sheet is applied to a central mounting or driving hub construction 24.

It is to be understood that the mounting hub construction shown is for purposes of illustration only as many other forms of construction are equally applicable.

As shown in Figures 4 and 5, the hub 24 has face plates 25 and 26 centrally apertured as at 27 for mounting on a drive shaft 28. The drive shaft has a reduced end portion 29 terminating at one end in an abutment shoulder 30 and at its other end in a threaded portion 31. A sleeve 32 embraces the shaft portion 29 between the face plates to maintain the plates in desired spaced relation. A nut 33 is threaded on the shaft and serves to clamp together the hub assembly.

A group of mounting pins 34, 34 are fixedly secured to one of the face plates, shown herein as the plate 25. The pins are spaced around a circle located between the center and periphery of the face plate. Openings 35, 35 are provided in the other face plate for slidingly receiving the pins 'therethrough. By this construction, the pins prevent relative rotary movement between the face plates and each form a carrier support for a folded polishing sheet.

As best shown in Figure 4, each folded sheet 20 is looped around a mounting pin with the ends of the sheet coextensively extending radially outward of the hub. As many folded sheets are applied as there are mounting pins to complete the polishing wheel. The entire periphery of the wheel is thereby made up of the ends of sheets each presenting a wavy or corrugated shape, the waves or corrugations of adjacent ends slanting in opposite directions. Pockets 36, 37, 38 and 39 are thereby formed in the folded arrangement of each sheet. The pockets 36 and 39 face each other and are open along their length from the mounting pin to the periphery of the wheel. Similarly, the pockets 37 and 38 are open along their length but extend away from each other. During the rotation of the polishing wheel, the resulting centrifugal force effects a constant flow of air radially outward of the wheel through the pockets thereby providing highly efficient ventilation.

When the periphery of the rotating polishing wheel 'en-" gages a work piece 40, shown in dotted lines in Figure 4, certain of the marginal edges of the folded sheets are bent generally normal to their original positions. This is diagrammatically shown in Figure 6. It will be noted that there is thereby provided numerous small abrasive areas for engaging a surface to be polished. These areas are on opposite sides of each loop which generally bend as at 41 and 42 away from the direction of rotation of the wheel. It will be noted that the portions 41 and 42 turn and expose, outwardly of the polishing wheel, opposite sides of the abrasive sheet. The portions so bent usually are of a maximum width of Ms inch to inch and of a length dependent on the peripheral length of the sides of the pocket. As the bent portions are relatively narrow for their length and are supported by the flexible body of the sheet, they become self-adjusting to completely engage a. contoured surface under a minimum of contact pressure and thereby are self-cleaning of any material removed from a surface during the polishing operation. Consequently, any heat generated by friction is minimized and is quickly dissipated by the improved ventilation previously described. As a result, only occasional lubrication of the abrasive surfaces is necessary and the possibility of glazing is eliminated.

It has been found in the operation of such a polishing wheel that the resistance to bending of the marginal edges is dependent on the stiffness of the abrasive sheet. To facilitate the quick bending as desired, rows of short slits 43, '43 may be provided as shown in Figures 6 and 7. Generally, the slits are located in the pleat areas of the sheet preferably at or near the initial point of contact with the work piece surface. Should the abrasive sheet be relatively flexible, slits only along the peripheral edges of the pockets are necessary and desirable. As many edge slits as desirable may be provided. If however, the sheet in relatively stiff and resistant to bending, then longer slits or rows of spaced slits are provided as shown. In any event, when slits are provided they should start along the initial working edge of the pleated or bunched sheet. In addition, the slits may be located in alignment lengthwise of the sheet or in staggered relation.

Shown in Figures 8 and 9 is a modified form of sheet 20a having an abrasive coating 21a. in this form, the pleats 44, 44 completely overlap each other to effect a folded sheet of the width of a single pleat. Before being mounted on a wheel the sheet is folded medially upon itself as at 23a. With this type of folded sheet, a wheel having the width of one pleat maybe formed by mount ing a single sheet on each mounting pin, or, a wheel of any desired width is possible by mounting folded sheets side-by-side on a mounting pin. in this form of construction, the abrasive working areas 45, 45 are bent from the sides of the pleats. As in the previously described form of sheet construction, bending slits f6 may be provided. Here, the slits are preferably located centrally of the sides of the pleats and/or at the bottom of the pockets.

With the several forms of folded abrasive-coated sheets shown and described herein, it has been found under certain conditions to be desirable to provide unccated spacer sheets 47, 4-7 in the pockets to separate adjacent coated surfaces and thereby prevent rubbing with resulting loss of abrasive material. Such spacers are shown in Figure 6. This provision is equally applicable to the form of folded sheet shown in Figure 9.

It is preferred, however, that abrasive-coated sheets 20, 20 be provided as shown in Figures ll and 12. Instead of abrasive coatings on the entire faces of the sheets as shown in Figure 10, the abrasive coating is omitted or removed as hereinafter described along a band or belt 50 extending medially across one or both faces of the sheet 20. This bare'center feature reduces the combined thickness of each sheet, when folded and doubled, at the base portion extending around a mounting pin as contrasted to the combined thickness of the remainder of the sheet. Accordingly, this construction permits the use of more abrasive sheets on each mounting pin than is possible with sheets having abrasive coatings over their entire surfaces. The important consideration is that, in the pleated element folded upon itself, the portion along and adjacent the fold line 23 be of lesser thickness than the portion nearer the marginal ends.

In forming the abrasive-coated sheet material with a bare-central portion, the abrasive may be omitted from such portion during the manufacture of the sheet or, if desired, may be removed from such portion of a completely-coated sheet by skiving as is done in the formation of coated abrasive belt joints, i. e. carefully removing the abrasive from such portion by the use of a grinding wheel or the like.

By the features described hereinabove, there is provided a polishing wheel having an efliciently ventilated and self-adjusting contact under relatively light pressure with the surface of a work piece to be polished. The result is to reduce the costs of operation by minimizing maintenance through replacement of abrasive sheets and by extending the working life of the wheel while at the same time effecting a complete polishing of surfaces, both fiat and contoured, in one direction which is of pleasing appearance to the eye.

It is to be understood that the forms of the invention, herewith shown and described, are to be taken as preferred embodiments of the same, and that various changes and modifications in form and structure may be resorted to Without departing from the spirit of the invention or the scope of the appended claims.

I claim as my invention:

1. In a polishing wheel having a hub for removably mounting polishing elements, the improvements in a polishing element therefor comprising a sheet of fibrous material, pleats in said sheet forming a wave-like edge, a fold medially of said pleated sheet whereby the sheet is folded upon itself, and a substantially uniform abrasive coating bonded on at least one face of the sheet, said face on which the coating is applied being uncoated throughout a relatively narrow band extending about and along the medial fold.

2. In a polishing wheel having a hub for removably mounting polishing elements, the improvements in a polishing element therefor comprising a sheet of fibrous material, pleats in said sheet forming a wave-like edge, a fold medially of said pleated sheet whereby the sheet is folded upon itself, and a substantially uniform abrasive face coating bonded on said sheet, the inner face of said folded sheet being uncoated throughout a relatively narrow band extending about and along the medial fold.

3. In a polishing wheel having a hub for removably mounting polishing elements, the improvements in a polishing element therefor comprising a sheet of fibrous material, pleats in said sheet forming a wave-like edge, a fold medially of said pleated sheet whereby the sheet is folded upon itself, and a substantially uniform abrasive face coating bonded on said sheet, the outer face of said folded sheet being uncoated throughout a relatively narrow band extending about and along the medial fold.

4. In a polishing wheel having a hub for removably mounting polishing elements, the improvements in a polishing element therefor comprising a sheet of fibrous material, pleats in said sheet forming a wave-like edge, a fold medially of said pleated sheet whereby the sheet is folded upon itself, and a substantially uniform abrasive face coating bonded on said sheet, the inner and outer faces of said folded sheet being uncoated throughout relatively narrow 'bands extending about and along the medial fold.

References Cited in the file of this patent UNITED STATES PATENTS 1,859,275 Bailey May 24, 1932 1,970,545 Chandler Aug. 21, 1934 2,070,322 Sperry Feb. 9, 1937 2,226,624 McFarland et al. Dec. 31, 1940 2,290,236 Hall July 21, 1942 2,574,037 Hendrickson Nov. 6, 1951 2,581,411 Hendrickson Jan. 8, 1952 

